Many contagious illnesses result from human inhalation of infectious, aerosolized particles. As used herein, an "aerosolized particle" is a particle which has become airborne within a liquid droplet or other airborne carrier (e.g., a dust particle). Infectious, aerosolized particles include bacterial cells, fungal spores, viruses, and other biological material. These infectious, aerosolized particles are referred to herein as "bioaerosols".
Viruses which can be transferred from human to human via an airborne route include rhinovirus, influenza virus, measles, rubella, and smallpox. Bacteria which can be transmitted via aerosols include staphylococcus aureus (staph infection) and legionella pneumonphila (Legionnaires disease). Aerosolized fungi can include, for example, Aspergillus which has been implicated as an airborne hazard in a hospital setting.
Infectious particles can become aerosolized, for example, when a person speaks, coughs, or sneezes. As more has been learned about the nature of infectious aerosols, researchers have discovered that various medical and dental procedures can generate bioaerosols as well. For example, infectious particles can become aerosolized when high-speed medical and dental machinery (e.g., dental scalers, bone saws, electrocautery procedures, and laser surgery) causes particle-containing droplets to be forced from a human or animal source. Infectious particles can also exist in vaporized water from cooling towers, water faucets, and humidifiers, for example. Spray irrigation which uses reclaimed waste-water also contains bioaerosols. Further, agricultural dust and airborne organic materials are likely to contain bioaerosols.
In order to protect humans and animals from preventable infectious illnesses resulting from the inhalation of bioaerosols, a need to detect and quantify bioaerosols exists. Detection and quantification of bioaerosols is an important first step in the identification and elimination of dangerous bioaerosols.
Several devices and methods for assessing airborne concentrations of viable microorganisms have been developed. Among the most simple of all methods is to place petri dishes with nutrient or selective media around the tested area. The bioaerosols attach to the surface of the nutrient agar plate and the level of bioaerosols in the environment can be inferred from the quantity on the plate.
Another method uses an Anderson Microbial Sampler (AMS) to collect bioaerosols. The AMS is a commercially available device having one, two, or six stages. For a multi-stage AMS, each successive stage has smaller through-holes. Because the through-hole size decreases with each stage, air drawn through the AMS accelerates at each stage. Less aerodynamic particles are trapped at the earlier stages.
A petri dish containing an agar medium appropriate for the microorganism being measured is placed in the AMS and a sample of air is drawn. The petri dish is then removed, inverted in its cover, incubated, and colonies enumerated.
The AMS enables particles to be sized aerodynamically, regardless of physical size, shape, or density. However, the AMS is relatively expensive. The expense of prior-art devices precludes widespread use of bioaerosol measurement devices, thus, the potential health benefits of such measurement devices generally remain unrealized
What is needed is an apparatus for measuring bioaerosols which is inexpensive, accurate, and has a simple design. Further needed is a non-invasive, simple method for measuring bioaerosols using such a device.